The present invention relates to a process for establishing point-to-multipoint connections and multipoint-to-point connections in a coupling field, comprised of a number of stages, each with a number of switching modules, each of which has a number of inputs and outputs that can be freely connected to one another. It is also directed to a related a coupling field, control device, and switching center.
The splitting of an incoming connecting line in a coupling field into a number of continuing connecting lines and the coupling together of a number of incoming connecting lines in another coupling field into a common, continuing connecting line are known in the field of SDH technology (synchronous digital hierarchy) from the ITU-T Recommendation G.841 (DRAFT) xe2x80x9cTypes and Characteristics of SDH Network Protection Architecturesxe2x80x9d, April 1995 version, FIGS. 5-7 (p. 51). In the coupling fields represented there, each coupling field input is connected to a number of coupling field outputs by means of a point-to-multipoint connection and a number of coupling field inputs are connected to one coupling field output by means of a multipoint-to-point connection. The represented use of at least two different and independent, i.e. redundant, connecting paths increases the transmission reliability in telecommunication networks or parts of them. A first pair that is comprised of a data source and a data sink indicated by arrows are connected by way of a first coupling field (xe2x80x9cmatrix connectionxe2x80x9d), two redundant transmission path pairs, and a second coupling field (xe2x80x9cmatrix connectionxe2x80x9d) to a second pair comprised of a data source and a data sink. The coupling fields mentioned are parts of SDH network nodes, so-called xe2x80x9ccross-connectsxe2x80x9d. The disposition of the transmission paths in pairs here is necessary for a transmission in full-duplex mode. For a transmission in half-duplex mode or for a unidirectional transmission, only one channel of each of the transmission path pairs would be required. The transmission path pair that is active for data transmission is called the SNCw connection (subnetwork connection working), the redundant transmission path pair is called SNCP connection (subnetwork connection protection). The transmission in one direction on each channel of the doubled transmission path pair will be represented below. In the opposite direction, the transmission is accordingly executed in reverse.
A data stream to be transmitted from the first data source to the second data sink is duplicated by the first coupling field and the data stream and its duplicate are transmitted to the data sink in parallel fashion, each on a channel of the redundant transmission paths SNCp and SNCw. Immediately upstream of the data sink, the data stream and its duplicate are received by the second coupling field on the redundant transmission paths and are coupled together. In so doing, the data stream and its duplicate are tested as to their quality so that as a result, if possible, a perfectly received data stream can be selected and conveyed to the data sink. If both of the redundant transmission paths do not fail or suffer interference simultaneously, then the data stream can be transmitted from the data source to the data sink in the above-described manner with a high degree of transmission quality and transmission reliability.
In conjunction with FIG. 1, first a situation is described that can result without the use of the process according to the invention. FIG. 1 shows a coupling field in three stages, each comprised of five switching modules, with currently used connections between the switching modules of the three stages. The coupling field is comprised of an input stage (I) with five switching modules 11, 12, 13, 14, and 15, an intermediary stage (II) with five switching modules 21, 22, 23, 24, and 25, and an output stage (III) with five switching modules 31, 32, 33, 34, and 35. Each of the respective five switching modules of the input stage (I) and the output stage (III) is connected to each of the five switching modules of the intermediary stage (II) via intermediary lines not shown in the FIG. However, connections that extend by way of these intermediary lines are in fact represented, so that a few intermediary lines can therefore be discerned indirectly. The intermediary lines are thus disposed between the input stage (I) and the intermediary stage (II) and between the intermediary stage (II) and the output stage (III). There is always an intermediary line between each output of a switching module of one stage and each input of a switching module of a neighboring stage. An intermediary line of this kind is used in FIG. 1, e.g. between the switching modules 11 and 21.
In the example represented, the switching modules each have five inputs and five outputs. One input of a switching module can be selectively connected inside the switching module to at least one output of the same switching module. An output of a switching module can likewise be selectively connected to at least one input of the same switching module. A switching module can simultaneously connect up to five independent connections between each of its inputs and each of its outputs. The switching modules 11 and 31 have this kind of a switching state. In these switching modules, like in most of the others of the coupling field, a direct switching through of the inputs and outputs is represented by horizontal lines between the inputs and the outputs. This is only intended to serve as a simple depiction.
If a connection through the coupling field of only one input of only one switching module of the input stage (I) leads to only one output of only one switching module of the output stage (III), then this reversible, definite connection is also called a xe2x80x9cunicast connectionxe2x80x9d. The xe2x80x9cunicast connectionsxe2x80x9d connected in FIG. 1 are represented by thin solid lines.
However, the connections described at the beginning are also possible, in which the data that are received by the coupling field on one of its inputs are duplicated and sent in parallel fashion on a number of its outputs. Here, constellations of this kind are called point-to-multipoint connections or xe2x80x9cmulticast connectionsxe2x80x9d. xe2x80x9cMulticast connectionsxe2x80x9d are depicted in the FIGs. with thick, dashed lines. A xe2x80x9cmulticast connectionxe2x80x9d of this kind is connected, for example, in the switching module 24 and on the input end, leads to the switching module 11 and on the output end, leads to the switching modules 31 and 32. Another xe2x80x9cmulticast connectionxe2x80x9d leads from the input A14 of the switching module 14, by way of the switching module 24 to the output A33 of the switching module 33 and to the output A34 of the switching module 34.
In a similar manner, a number of inputs of a coupling field can also be coupled together with a single one of its outputs into a connection that is called a multipoint-to-point connection here or is also called a xe2x80x9cmerge connectionxe2x80x9d. xe2x80x9cMerge connectionsxe2x80x9d are represented in the FIGs. with thick, solid lines. The switching module 25 couples one such xe2x80x9cmerge connectionxe2x80x9d together between its inputs toward the switching modules 11 and 12 and its output toward the switching module 31. Another xe2x80x9cmerge connectionxe2x80x9d is produced between the inputs B14 and B15 of the switching modules 14 and 15 by way of the switching module 25 to the output B35 of the switching module 35. In a xe2x80x9cmerge connectionxe2x80x9d, the data stream and its duplicate, which have been received in parallel on the input end by the coupling field, are tested as to their quality by the coupling switching module. If the data stream or its duplicate have been identified as error-free, then a single error-free data stream is selected and conveyed further to a single output. If neither the data stream nor the duplicate are error-free, then an error-encumbered data stream, possibly additionally marked especially because it contains errors, could also be supplied to the output.
Duplicated data streams are preferably transmitted on different line bundles. For incoming data streams, these line bundles then feed to different switching modules of the input stage (I) or for outgoing data streams, they begin at different switching modules of the output stage (III). xe2x80x9cMerge connectionsxe2x80x9d are advantageously already connected together in switching modules of the intermediary stage (II) in order to load only intermediary lines between the input stage (I) and the intermediary stage (II) with duplicated data streams and not the intermediary lines between the intermediary stage (II) and the output stage (III). Likewise, it is useful to split the xe2x80x9cmulticast connectionsxe2x80x9d first in the switching modules of the intermediary stage (II) since only the intermediary lines between the intermediary stage (II) and the output stage (III) have to carry duplicated data streams. The coupling together of xe2x80x9cmerge connectionsxe2x80x9d and splitting of xe2x80x9cmulticast connectionsxe2x80x9d can also occur in switching modules of other stages of a coupling field, particularly also in coupling fields with more stages than in the coupling field shown in FIG. 1. In any case, as early a coupling as possible and as late a splitting as possible are advantageous.
From the arrangement of the connections in FIG. 1, for the switching module 24, it turns out that through the reduced utilization of the number of inputs in relation to the number of outputs, only the output to the switching module 35 remains usable. As a result, the connection a between switching module 12 and 24 is only continued on the switching module 35 and its outputs, but not on the outputs of the other switching modules of the output stage (III). The part of this xe2x80x9cunicast connectionxe2x80x9d leading to the intermediary stage (II) is represented by a dashed, thin line in FIG. 1. A blocking inside the coupling field occurs if, due to a connect request, the connection a, which is represented in FIG. 1 by a dot-and-dash line, is intended to be conducted on an output of the switching modules 31-34.
A similar problem arises for the sole, as yet unoccupied output line b from the switching module 32. This line can be reached with the circuit arrangement represented in FIG. 1 by way of the switching module 25. The switching module 25, though, has only a single input free in FIG. 1, namely the one to switching module 13. When there is a connect request from one of the free inputs of the remaining switching modules of the input stage (I) toward the free output line b, another blocking occurs.
The object of the invention is to establish point-to-multipoint connections and multipoint-to-point connections in a coupling field of the type mentioned, taking into consideration the respective blocking probability.
This object is attained by a process for establishing point-to-multipoint connections and multipoint-to-point connections in a coupling field comprised of a number of stages, each with a number of switching modules, each of which has a number of inputs and outputs that can be freely connected to one another, wherein when there are switching modules in at least one stage in the coupling field, and if, depending on their type, these switching modules are capable of simultaneously splitting point-to-multipoint connections and coupling together multipoint-to-point connections, then point-to-multipoint connections are split by those switching modules in which more inputs than outputs are already loaded with connections and multipoint-to-point connections are coupled together by those switching modules in which more outputs than inputs are already loaded with connections.
It is also attained by a coupling field, which contains a number of stages, each with a number of switching modules each of which has a number of inputs and outputs that can be freely connected to one another, and a control device, wherein in at least one stage in the coupling field, there are switching modules which, depending on their type, are capable of simultaneously splitting point-to-multipoint connections and of coupling together multipoint-to-point connections, and that the control device permits the splitting of point-to-multipoint connections by those switching modules in which more inputs than outputs are already loaded with connections and permits the coupling together of multipoint-to-point connections by those switching modules in which more outputs than inputs are already loaded with connections.
It is further attained by a control device for a coupling field, which contains a number of stages, each with a number of switching modules each of which has a number of inputs and outputs that can be freely connected to one another, wherein in a coupling field of this kind, in which in at least one stage, there are switching modules which, depending on their type, are capable of simultaneously splitting point-to-multipoint connections and of coupling together multipoint-to-point connections, the control device permits the splitting of point-to-multipoint connections by those switching modules in which more inputs than outputs are already loaded with connections and permits the coupling together of multipoint-to-point connections by those switching modules in which more outputs than inputs are already loaded with connections.
It is also attained by a switching center with a coupling field, which contains a number of stages, each with a number of switching modules each of which has a number of inputs and outputs that can be freely connected to one another, and a control device, wherein in a coupling field of this kind, in which in at least one stage, there are switching modules which, depending on their type, are capable of simultaneously splitting point-to-multipoint connections and of coupling together multipoint-to-point connections, the control device permits the splitting of point-to-multipoint connections by those switching modules in which more inputs than outputs are already loaded with connections and permits the coupling together of multipoint-to-point connections by those switching modules in which more outputs than inputs are already loaded with connections.
Other advantageous embodiments of the invention can be inferred from the dependent claim and the description.